works. But I can not say that good condensation will prevent naphthalene. When we use naphtha, or whatever we may use throughout our works, we simply remove the obstruction which we have caused, and then we go right on again and make the same obstruction afterwards. Naphthalene is the only substance in gas which can crystallize. By adding the vapors we simply try to carry in solution naphthalene and prevent its crystallization. By the high heats used to-day we do undoubtedly form more naphthalene than we did 30 years ago. When we were satisfied with a yield of 31⁄2 to 4 feet per pound of coal we did not hear anything about naphthalene troubles anywhere. The oldest gas men in this Association will tell you that in those days they knew nothing about naphthalene. But we do know about it now. In the earlier days we simply carried off the light oils, allowing them to remain in the gas, and this kept the naphthalene in suspension. That is my theory, and it is the result of my experience. MR. ODIORNE-I would like to ask Mr. Gimper just how he introduced naphtha into the pipes.

MR. GIMPER-At the outlet.

MR. ODIORNE-Under pressure?

MR. GIMPER--No; simply under gravitation. We introduced it in the main on top of the inlet, for naphtha.

MR. DOTY-I believe, generally speaking, that gas naphtha at a temperature of 50° F. will not absorb naphthalene at all.

MR. GIMPER-In our gas we always used naphtha, and always removed the naphthalene from it.

MR. DOTY-At what temperature?

MR. GIMPER—At the ordinary temperature.

MR. DOTY-At 160° F.?

MR. GIMPER-No; at a lower temperature. But in works where the stoppages may be large we use steam with it.

MR. DOTY-In our experiments at 50° F. we obtain more naphthalene from the gas naphtha than we put into the liquid. That is, if we put in 50 per cent. by weight of naphthalene in solution at 110° F. and then reduced the temperature to 50° F., and weighed the naphthalene deposited, we found more naphthalene than we had put in.

MR. GIMPER-I do not believe that gasoline introduced into the works and allowed to pass through the scrubbers and purifiers. and into the holders will prevent naphthalene stoppages, because the tar coating which is in the inside of our pipes will absorb the gasoline again, and we simply pump it out at our drips.

MR. RUNNER-We have had some little experience with naphthalene which may be of interest. A year or two ago we made

some changes in our works, putting in full-depth benches, and our naphthalene trouble then commenced. My first attempt in handling it was in putting in an apparatus to employ benzine, benzole or gasoline, using a steam coil in the tank to raise it to a high temperature and vaporize it. We passed sufficient gas through his tank, by-passing the governor, to carry from three to four gallons of naphtha with every 20,000 feet of gas. As long as we did that we had no naphthalene trouble in any part of the main, but inside of 24 hours after we stopped we were blocked. As to the condensation to which Mr. Gimper refers, I think it very necessary to have gas condensed at certain temperatures in order to retain the naphthalene properties in it. A year ago, while trying to get rid of the constant expense of injecting benzine into the gas, we added to our condenser a new scrubbing apparatus, put thermometers at each outlet, and had the temperature frequently taken at those points. We found that as long as the temperature was maintained at a certain point we had no trouble from naphthalene, but if not constantly watched and kept at those points it would show traces at once. Before putting in the additional scrubber and condensing plant we kept four men busy on the street with benzine cans keeping the naphthalene trouble down so as to give any kind of service at all; but as soon as we introduced those improvements in our condensing and scrubbing outfit we no longer had any naphthalene troubles, although it covered the period of the year when we had the most severe strain on the works.

THE SECRETARY-At what temperature of the gas did you find the naphthalene troubles disappear?

MR. RUNNER-We have an air condenser, washer, multitubular condenser and another washer. If the gas was allowed to pass through the multitubular condenser at too high a temperature we were sure to have naphthalene troubles; but if we kept the temperature at from 60° to 65°, we had no trouble at all. If we allow it to run up to 68° or 70° or 72° we are sure to see traces of naphthalene.

THE PRESIDENT-We would like to hear from Mr. Barthold the results of his experience.

MR. BARTHOLD--When admitting uncarbureted water gas into the retorts of three benches of the seven in operation, to the extent of 2 per cent. of the total gas made, there was a decrease of 3.5 candle feet, or about 7 candle; with 3 per cent. a decrease of 6.1 candle feet, or about 1.2 candle; with 7.2 per cent. a decrease of 8 candle feet, or about 1.6 candles. With 5 per cent. of carbureted water gas there was a decrease of 1.7 candle feet or 34 candle,

and with 5.3 per cent. coal gas from the scrubber outlet a decrease of 1.5 candle feet, or 3 candle. The three benches were on one section of the hydraulic main. While admitting water gas into these benches the crude gas was tested for ammonia, samples being taken from the foul main close to the hydraulic main outlet. An average of six tests of the coal gas at this point gave 2,933 grains of ammonia per 1,000 feet. An average of four tests with about 10.5 per cent. of uncarbureted water gas gave 2,776 grains per 1,000 feet. An average of 4 tests with about 12.5 per cent. carbureted water gas, gave 2,699 grains per 1,000 feet. The results corrected for 100 per cent. coal gas give: Coal gas, 2,933 grains per 1,000; with 10.5 per cent. uncarbureted water gas, 3,102 grains per 1,000; with 12.5 per cent. carbureted water gas, 3,084 grains per 1,000, which shows a slight increase from the admission of water gas.

(1) With coal gas, yield 5.14, candle power 16.4; (2) with 5.1 per cent. uncarbureted water gas, yield 5.1, candle power 15.4; (3) with 5 per cent. carbureted water gas, yield 5.05, candle power 16.3.

THE PRESIDENT-Has Mr. Slater something to offer us on this subject?

MR. H. C. SLATER-I can not say anything especial on this subject. As far as I know in Milwaukee we have had no trouble in the street and none in the works, except in two instances: Once in the connections to one of the station meters, and the other in the inlet to one of the holders. The naphthalene is pretty much all taken out of the gas in our condensers. The temperature of the outlet of the condenser is about 70° F. I have had no trouble with naphthalene except in taking it out of the condensers.

THE PRESIDENT-Has Mr. Mitchell anything to say on this subject?

MR. MITCHELL-I do not know that I have anything new to say. It has been our practice to try to keep in the gas as much of the light oils as possible, and in that way dissolve and carry along the naphthalene. Naphthalene is a very valuable illuminant, and it is our object to carry it along if possible to the burners. We are working along that line now; we expect at some meeting of the Association to show how we do it. We are getting pretty good results and are not having much trouble with naphthalene in our present apparatus; but we have not yet run it long enough to be positive of the results.

THE PRESIDENT-At the time you read your paper before the American Association you thought the Shadbolt method a sure prevention, did you not?

MR. MITCHELL-There is no question but that method did work well with us while running on coal gas; but after we put in operation our new water gas apparatus we were unable to get the same results. We just simply quit, closed the valves, and the apparatus is standing there yet. While making coal gas there is no question but that it did the work. The gas partially purified on being caused to return would take up some of the lighter oils or benzoles of the coal tar and carry them along, and they would act as solvents for the naphthalene and carry it to the burners. There is no question but that the Shadbolt process did work well with us. We had been so bothered with naphthalene that it sometimes took four or five barrels of gasoline every 24 hours to get the holder inlet clean, so we could get the gas into the holder. By means of the Shadbolt process we stopped all use of gasoline.

MR. H. C. SLATER-With reference to the use of naphtha or light oils to carry the naphthalene along. Has anyone made any tests to show that naphthalene is carried to the burners? Or is the naphthalene condensed and pumped out in solution at the drips?

MR. ODIORNE-I would like to ask Mr. Doty if naphthalene is more apt to cause difficulty and bother at certain times of the year. or at one time more than at another?

MR. DOTY-Unquestionably, for temperature is a very important factor.

MR. ODIORNE-At what time of the year did Mr. Doty have the most trouble?

MR. DOTY-At the changes of the seasons: particularly at the change from summer to fall. But just when or where you are going to get it no one knows.

MR. CHOLLAR-I think we might ascribe a good deal of the trouble with naphthalene to its very high molecular weight which

carries with it very low specific heat. The vapor of naphthalene would weigh, per volume, I would say, 64, as against an equal volume of air, at about 14; and a very slight increase of heat will change it from a solid to a vapor. In that respect it is like camphor, which takes the form of vapor directly from the solid. Therefore, about the only practicable way to control it is to keep it in solution with some other vapor.

MR. MITCHELL--Does Mr. Chollar believe that it can be carried along to the burner?

MR. CHOLLAR-Undoubtedly.

MR. MCCLARY--I may be able to add a word concerning the probability of the naphthalene being carried forward and consumed at the burner. The Ogden Gas Company, Chicago, had some trouble from naphthalene in services last fall. We were getting our oil from the Standard Oil Company and, as all other conditions so far as we knew remained unchanged, we complained to the Standard Oil Company which sent its expert at the Whiting refinery (Dr. Gray) who made a careful examination of our works and methods, but was unable to diagnose the case. We were at that time rigging one of those little vaporizers such as had been referred to by a previous speaker, and upon Dr. Gray's recommendation we used 74° naphtha in it. As I have said, our stoppages were all in the consumers' services. We had no trouble at the works, so we connected the vaporizer, or the naphthalene preventer as we called it, with the outlet of the governor. While I did not positively know what it did or did not accomplish, yet after we put it in we had no further trouble. Such troubles are intermittent, and this may have been a coincidence, but it is a fact that none of the naphthalene which was supposedly carried forward in the gas ever reappeared in the drips or elsewhere. If there was, during the time we were operating the preventer, any napthalene present in the gas after it passed the governor it was burned. When running the preventer we used about two barrels. of naphtha daily. It evaporated at a temperature of 185° F., under which temperature the two barrels would last about 24 hours. Whenever naphthalene crystals formed in the purifiers. we immediately started up the preventer for a day or two and had no further trouble. One of the experiments which we tried was for the purpose of ascertaining whether this naphtha vapor did dissolve the naphthalene scale. We filled a large glass tube with large naphthalene crystals which we had taken from the dome of the purifier (the only place about the works where naphthalene crystals appeared) and passed the gas, previously cooled by carrying the pipe outside the building, through it. The glass tube